Stability and deformation of mine waste dumps in north-central Nevada.

摘要

The major aspects of the dissertation were: (1) collection and testing of mine waste materials to establish strength and other engineering parameters for a range of typical mine waste materials; (2) application of limit equilibrium slope stability methods to mine waste piles; and (3) application of finite difference and finite element methods to study the stability and deformation of mine waste piles; (4) comparison of slope failure and deformation features observed in the field with such features produced in computer models.; Sixteen bulk samples of mine waste rock were collected from six mine sites in north-central Nevada. Testing included grain size distribution analysis, evaluation of constrained modulus, direct shear testing, point load testing of lump samples, and slake-durability testing. Based on the testing, constrained modulus values were found to be stress dependent, with higher modulus values associated with increased confining stress on the samples. Evaluation of direct shear testing data demonstrates that strength parameters for these materials may be interpreted as linear (C plus phi) functions or non-linear (phi only) functions. Non-linear strength values at 1 atmosphere confining pressure (14.7 psi) ranged from {dollar}phi = 35spcirc{dollar} to {dollar}phi = 51spcirc.{dollar}; Parameter variation/sensitivity studies were made using the Simplified Bishop's method and the computer program XSTABL. These studies demonstrate the influence of basic parameters on the factor of safety of a mine waste dump. Extending these studies, the factor of safety was found to be higher using interpreted linear (C plus phi) strength values compared to non-linear (phi only) values for the same soil.; Finite difference and finite element models of mine waste piles were developed using the computer programs FLAC and FEADAM84. The finite difference models simulate either a completely built waste pile or incrementally built pile. These models show different failure modes, depending on the simulated strength of waste pile materials. Development of zones of tensile stress near the top of the model as a result of compression or slope face instability demonstrate the potential for development of surface cracking, such as that observed in the field.; The finite element model developed for the project contained 544 elements and simulated construction in 40 incremental layers. This model demonstrated that the development of imbricate or stairstep faulting near the crest (as observed in the field) could be modeled. Development of a zone of tensile stress and potential tension cracking near the dump-surface was found to be due to downward and outward displacements of newly placed materials near the dump crest and the effect of this movement on adjacent interior soil elements. (Abstract shortened by UMI.)